when i did twice it made bang (more of a pop) and some smoke (smelt like electrical burning) came out of the bonnet, both time the spark plug on the cylinder (furthest away from radiator) had its gap completely closed

changed the plugs and put the leads in correct order
and car will start but die after a few seconds, or if i rev it as soon as i let go

any ideas what could be wrong
could i have damaged the coil pack or leads?
how could i test - leads have resistance